3.08 Predicting products of electrolysis

Question 1

Write the equation for the dissociation of water

Answer 1

H2O <—-> H+ (aq) + OH- (aq)

Question 2

In electrolysis, if the metal cation is more reactive than H+, what will be produced at the cathode?

Answer 2

Hydrogen

Question 3

In electrolysis, if the metal cation is less reactive than H+, what will be produced at the cathode?

Answer 3

Metal

Question 4

In electrolysis, if halide ions are present, what will be produced at the anode?

Answer 4

Halide molecules

Question 5

In electrolysis, if halide ions are NOT present, what will be produced at the anode?

Answer 5

Oxygen and water

Question 6

Write the half equations for the electrolysis of copper chloride solution

Answer 6

Cathode: Cu2+ + 2e- —-> Cu

Anode: 2Cl- —-> Cl2 + 2e-

Question 7

Write the half equations for the electrolysis of sodium chloride solution

Answer 7

Cathode: 2H+ + 2e- —-> H2 (as sodium is more reactive than hydrogen)

Anode: 2Cl —-> Cl2 + 2e-

Question 8

Write the half equations for the electrolysis of sodium sulfate solution

Answer 8

Cathode: 2H+ 2e- ….> H2

Anode: 4OH- —-> O2 + 2H2O + 4e-